Method and apparatus for operating wells



Y Sept. 24, y R l. BROWN METHOD AND APPARATUS-.FOR OPERATING WELLS FiledOct. 4. 1938 393 Hg@ F155 F16 Patented Sept. 24, 1940 UNITED STATESPATENT OFFICE Richard I. Brown, Los Angeles, Calif., assignor toStandard Oil Company of California, San Francisco, Califv, a corporationof Delaware Application October 4, 1938, Serial No. 233,257

21 Claims.

This invention relates to apparatus and method for casing and completingwells, such as oil and gas wells.

In many instances a. well, such as an oil or gas well. penetrates morethan one productive zone. One of the major diiculties in-using a singleoil well to produce simultaneously from a plurality of productive zonesis that the productive zones are usually separated by zones containingwater.

It is necessary in such instances to seal such last mentioned zones toprevent the communication of such water to the upper and lower*productive zones. The diiculties of producing from more than oneproductive zone simultaneously are such that in many instances no eiortis made to produce from other than the lowest productive zone. In suchcases, the necessary surface, water and oil strings are placed in thewell to the deepest productive zone, and the upper productive andunproductive zones are cemented o.

One method of producing from more than one productive zone is to runcasing from the top of the well to its bottom and to endeavor to obtainthe necessary water shut-offs by cementing of the string in the well.When such cement jobs have been completed the casing opposite theproductive zones is gun-perforated. One of the disadvantages ofsuch'method is that it is difcult thereby to obtain adequate andsatisfactoryperforationsV to permit the productive zone to produce inquantities approaching its maximum capacity, by reason of the fact thata large portion of the zones face is blocked by cement or blank portionsof the oil string.

'I'his invention comprehends broadly an arrangement of alternatesections of casing, usually of a hard material such as steel at pointsopposite unproductive zones, and of a softer .drillable material atpoints opposite the zones 40 from which production is desired, togetherwith a mode of supporting these sections in spaced relation during theirintroduction and cementing, followed by a selective removal of one crmore of the drillable sections to produce the oil or gas from thedesired zones or strata.

It is an object of this invention to provide a simple and expedientapparatus and method for multi-zone production.

Another object of this invention is to provide a convenient method in amultiple zone well of opening the productive zones to the well andblocking the non-productive zones or zones from which production is notdesired.

.Another object of this invention is to increase -Y the flow of iiuidfrom zones from which production is desired.

These and other objects and advantages will be more fully apparent fromthe following description and from the accompanying drawing which form apart of this specification and illustrate a preferred embodiment of thisinvention.

In the drawing:

Figure 1 represents a vertical and part sectional `view of a Wellshowing location of the oil string with respect to various strata.

Figure 2 is a vertical sectional view of the well of Figure 1, whereinthe soft or drillable casing has been removed opposite the zones fromwhich production is desired.

Figure 3 is a vertical sectional View of an oil string illustrating avariation of the means for supporting and removing the drillablesections of Figure 1.

Figure 4 is a vertical sectional view of an uncemented oil stringillustrating a further variation of the method partially illustrated inFigures 1 and 3, in which the drillable sections are reinforced duringtheir insertion into the well bore.

Figure 5 represents a Vertical sectional View of an uncemented oilstring showing a further variation of the general method partially shownin Figures 1 and 3, in which the drillable sections are entirelyomitted.

Figure 6 is a vertical sectional view of a cemented oil string with aperforated secondary liner illustrating an advanced stage of the generalmethod illustrated in Figures 1, 3 and 5, especially in combinationvwith the stage illustrated in Figure 2.

In the drawing: Figure 1 indicates a fragmentary portion of a string ofcasing'in an oil or gas well. Such portion, being that which penetratesthe producing zones, is known in the art as the oil string, todifferentiate it from the upper, water and surface strings. The oilstrings shown in Figures l, 2, 3, 4 and 5, being the outer oil strings,will be called primary oil strings to differentiate them from an oilstring within such primary oil string, herein called a secondary oilstring, as shown in Figure 6.

The well is indicated as passing through si'x different strata, zones,or formations, 2, 3, 4, 5, 6, l. Strata 2, 4 and 6 are non-productivestrata, or strata from which production is not desired. Formations 3, 5and 'l are formations from which production is desired.

The casing is shown to be secured in the hole by the cement 8, which maybe introduced by any conventional method. The primary oil string in 55the drawing is shown to comprise a number of divisions equal to thenumber of strata. Such divisions of the primary oil string are 9, IU, II, I2, I3 and I4. Each such division of casing is composed of one ormore joints or sections of casing not individually shown in the drawing,suicient to give each division the desired length.

The divisions of the primary oil string, 9, I I', I3, opposite theportions of the well which are nonproductive, are made up of sections ofnormal oil well casing.

The divisions of the primary oil string, I0, I2 and I4, opposite theportions of the well from which production is desired, are made up ofsections of drillable casing, which may be an aluminum alloy or the likeas will be discussed in greater detail below.

All the sections of the primary oil string are joined in normal fashionsuch as by threads or by weldings, not shown in the drawing.

Referring to Figure 1 of the drawing, the location and depth of theproductive and non-productive intervals being known, the primary oilstring I is run into the well hole in such manner that sections I0, I2and I4 of such oil string face productive intervals 3, 5 and 1, andsections 9, II and I3 of the oil string face non-productive intervals 2,4 and 6.

As shown in Figure 1, all lengths of the primary oil string are of thesame diameter. However, the sections of such string 9, II and I3,opposite non-productive intervals 2, 4 and 6, are normal casing, but thesections of thev string I0, I2 and I4, opposite productive intervals 3,5 and 1, are made of softer, drillable casing.

After the primary oilstring has been cemented in the well hole by anydesired method, during which the primary oil string may be moved toprevent channeling of the cement, and after the cement has set, thedrillable sections of the primary oil string are removed by any desiredmethod. Such removal may be accomplished by van under-reamer,explosives, abrasives, or chemicals, for instance. Wherethe sections ofthe normal and drillable casing are of the same size as shown in Figure1, an expansion type drilling tool may be used to drill up the drillablepipe. In that portion of the hole from which the drillable pipe has beenremoved, the cement, mud and other undesired substances are then alsoremoved, by any desired method, such as wallscraping or under-reaming.

This results in a well having normal casing cemented opposite thesections of the well which are unproductive, or from which it is notdesired to produce, and no casing opposite the zones from which it isintended to produce oil or gas or other desired substances.

Figure 2 illustrates the appearance of the well and casing after thewell has been completed as described under Figure 1. The drillablesections I0, l2, I4 have been removed and the cement and mud formerlysurrounding such drillable Sections have also been removed. The sectionsof normal casing, 9, II and I3 remain in place, surrounded by cement tohold such sections in place and to prevent flow of undesired substancesfrom the strata 2, 4 and E.

Figure 3 shows a modification of the method and apparatus illustrated inFigures 1 and 2. As shown in Figure 3, the softer drillable sections I5,I6 and I1 of the primary oil string are of smaller diameter than thenormal casing 9, II and I3 opposite the intervals desired to beexcluded. This reduction of the size of the drillable Casing.

which may be accomplished by any desired method, as by use of drillablereducers, has numerous advantages, the most important of which is thatit facilitates the removal of such drillable casing. The method ofdisposing of the drillable pipe I5, I6 and I1, as illustrated in Figure3,

may be accomplished by use of a bit small enough, even in its expanded,operable condition, to pass freely through the normal casing sec-1 tions9, II and I3. When the bit, with a diam eter slightly smaller than thediameter of the normal casing 9, II and I3 strikes, the sections of thesmaller-sized drillable casing, its cutting, drilling eect will beoperative. Except for the smaller diameter of the drillable casing themethod illustrated by Figure 3 operates in much the same manner as thatillustrated in Figure 1. When the drillable sections I5, I6 and I1 andthe cement surrounding them are removed the appearance of the well, ascompleted, is similar to that shown in Figure 2.

Figure 4 illustrates a variation of the method and apparatus shown inFigures 1 and 3. Drillable casing, such as is indicated for use instrata, 3, 5 and 'I is obtainable with remarkable tensile strength.However, in some instances where the depth of the well hole between therst section of drillable casing and the last is considerable,

the tension placed upon such sections of drillable casing is such thatthe safety factor in tension is lower than a desired value. In suchcases the safety factor may be raised by suitably fastening an inner,hard wash pipe I8 inside of the primary oil string, preferably runningfrom above the topmost section of drillable casing to below thebottom-most section of drillable casing. The tension of such division ofthe oil string is then partially carried by the wash pipe.

In Figure 4 the wash pipe is indicated by I8 and is shown connected withthe primary oil string by appropriate means at I9 and 20. 'I'he sectionsof normal hard casing are indicated, as in Figures 1, 2 and 3, by 9, IIand I3, and the sections of drillable casing by I0, I2 and I4 as inFigure 1.

In the embodiment here shown in Figure 4, the sections of drillablecasing, I0, I2 and I4, are of the same diameter as the sections ofnormal hard casing, 9, II and I3. However, the use of smaller diameterdrillable casing, as shwn in Figure 3, may also be used in conjunctionwith the use of the reinforcing wash pipe.

In addition to reinforcing the oil string in tension, the wash pipe I9may also permit the circulation of uids through it.

After the primary oil string has been emplaced, as shown in Figure 4,from the lowest producing zone to above the highest, the string may becemented in any desired manner. When the cement has hardened suiciently,the wash pipe may be separated from the attachments I9 and 20 andremoved from the well. When this has been accomplished, the drillablesections of the string IIJ, I2 and I4 and the cement and mud surroundingthem may all be removed as described under Figure 1, and the appearanceof the treated portion of the well will lthen be as shown in Figure 2.As used herein, by the term wash pipe is meant a string or section ofpipe or casing of smaller diameter than the primary oil string placedand fastened longitudinally within the primary oil string assembly.

Referring to Figure 5, as in Figures 1, 2, 3 and 4, strata 3, 5 and 1are strata from which production is desired, and strata 2, 4 and 'Ii arestrata which are desired to be shut off from the well. In Figure 5,sections of normal hard casing, S, I I and I3, are suitably fastened byconnections 2|, 22, 23, 24 and 25, at predetermined intervals,

' on sections of smaller diameter wash pipe i8.

After the well hole has been drilled the wash pipe, with the sections ofnormal hard casing suitably fastened, as above described, are run intothe well in such manner that the sections of normal casing 9, II and I3are opposite the strata desired to be excluded, and the strata fromwhich production is desired' 3, 5 and 1 are bare. Figure shows suchassembly before the sections of normal casing 9, II and I3 have beencemented. At such stage, as in the similar stage shown in Figure 4, theiow of substances from productive zones is precluded 'by the hydrostaticpressure of uidsin the well, not shown in Figures 4 and 5.

The sections of normal casing 9, and I3 are then cemented in any desiredmanner, as by the forcing of cement down the wash pipe, out at thebottom and up the well above 9. When the cement has hardened the washpipe may be cut free from its fastenings and removed from the well or itmay be drilled up. The cement and mud opposite the strata 3, 5 and 1,from which it is desired to produce, are then drilled out. When this hasbeen accomplished the appearance of the well is essentially the same asrepresented in Figure 2.

Figure 6 illustrates a variation of the apparatus and method disclosedin Figures 1, 2, 3, 4 and 5. When the well has been completed by usingany or all, or combinations of, the processes and ap# paratus shown inFigures 1, 2, 3, 4, and 5, so that the appearance of the well at suchstage is essentially that shown in Figure 2, there may be placed in thewell a string of smaller diameter casing 35 containing appropriatelyspaced perforated portions 21, 29 and 3| and appropriately spaced blanksections 26, 28 and 30. This inner string of smaller diameter casing 35,which may be called the secondary oil string, is held in place by anyappropriate means, as by an appropriate base, and by the packers 32,33and 34, which packers 32, 33 and 34 also serve the function ofpreventing the passage of substances through the annulus between thesections of normal casing 9, II and I3 and the secondary oil string 35.The perforated portions 21, 29 and 3| of the secondary oil string 35permit the ow of substances into the secondary string 35 and up thewell.

Packers and other devices may be placed inside the blank sections 25, 28and 30 of the secondary oil string to govern or'control the productionfrom the various zones or portions of zones. Thus, a packer placedinside of the blank section 28 of the secondary oil string could, whendesired, preclude production from strata-5 and 1, entirely or in part.

In the event it is desired to shut off any productive strata by reason,for instance, of encroaching water or undesirably largevolumes of gas,blank pipe with a diameter smaller than that of the secondary oil string35 ma'y be placed opposite the strata to be shut o, and may be heldthere by packers suitably placed to prevent fluid from said strata fromhaving access to the well, or said blank pipe with smaller diameter maybe cemented into place, to prevent ilow from the productive stratumdesired to be excluded. Such method of shutting oif productive stratamay be adopted either in the embodiment shown4 in Figure 6 or in Figuresl, Z, 3, 4 and 5.

The secondary oil string may be made of drillable material or ofordinary steel pipe. 'Ihe use of the drillable material here has theadvantage that if the perforated portions 21, 23 and 3| become cloggedwith sand they may be drilled out and the portions of the Well adjacentto them be cleaned and scraped before operations are resumed, afterhaving replaced the secondary liner. Or if productive strata 3, 5 and 1cease to be productive, the secondary oil string may be drilled up andoperations carried to lower productive horizons.

Where reference is made herein to normal casing there is meant the typeof casing normally used in oil wells, such as Wrought iron, welded andseamless steel casing. While such casing is drillable to some extent, bydrillable casing as usedherein is meant casing and oil string partswhich are readily and easily drilled. Such alloy material is nowavailable to the oil industry. It has high tensile strength and burstingpressures and its resistance to collapse, corrosion and abrasioncompares favorably with common steel casing. Inasmuch as the specicgravity of such alloy drillable casing is approximately the same asshale, when it is drilled up the cuttings are carried away by thecirculating ulds. Drillable casing is obtainable which can be drilled upas rapidly as twenty-five feet per hour. By drillable casing, therefore,is meant casing which, as distinguished from ordinary steel casing, isreadily drillable and yet possessed of the characteristics necessary toperform its functions.

Drillable casing and oil well equipment of the nature described above isnow obtainable in desired shapes and sizes composed of aluminum alloys.One such alloy suitable for manufacture of drillable oil well casing iscomposed of 0.7% silicon, 1.3% magnesium, 0.25% chromium, and theremainder of aluminum and aluminums normal impurities. Aluminum alloy ofsuch composition is obtainable with the following characteristics:

Specic gravity 2.69 Weight, lbs. per cu. in 0.097 Thermal conductivityat 100 C., C. G.

S. units .37 Average coefficient of thermal expansion per degreeFahrenheit:

(5S-212 F 0.0000130 68-392" F 0.0000136 68-572 F 0.0000141Elongation--percent in 2 inch round specimen 0.505 in. diam 20 Hardness,Brinell 500 kg. 10 mm. ball 80 Shearing strength, lbs./in 26,000Endurance limit, lbs/sq. in 11,000

Yield Tensile Elongation Temps., F. strength, strength, in 2 inches,

. q. in lb./sq. in. percent While the methods and apparatus for casingand completing wells herein described are well adapted to carry out theobjects of the invention, it is understood that various modificationsand changes may be made without departing from the invention, and theinvention includes all such modifications and changes which come withinthe scope of the appended claims.

I claim:

1. A method of operating a well comprising lowering into the well astring of casing made up of sections of normal casing and sections ofdrillable casing of smaller diameter than the normal casing, so that thesections of normal casing are substantially opposite portions of thewell from which no production is desired and the sections of drillablecasing of smaller diameter are substantially opposite portions of thewell from which production is desired, cementing such string of casingin the well, drilling away the sections of drillable casing fromportions of the well from which production is desired, and baring thesurfaces of the portions of the well from which the drillable casing hasbeen removed and from which production is desired.

2. A method of operating a well comprising lowering into the Well astring of casing made up of sections of normal casing and sections ofdrillable casing of smaller diameter than the normal casing, so that thesections of normal casing are substantially opposite portions of thewell from which no production is desired and the sections of drillablecasing of smaller diameter are substantially opposite portions of thewell from which production is desired, cementing such string of casingin the well, drilling away the sections of drillable casing fromportions of the well from which production is desired, baring thesurfaces of the portions of the well from which the drillable casing hasbeen removed and from which production is desired1 and lowering throughthe remaining sections of normal casing a perforated inner string seatedopposite portions of the well from which production is desired.

3. A method of operating a well comprising lowering into the well astring of casing made up of sections of normal casing and sections ofdrillable casing so that the sections of normal casing are substantiallyopposite portions of the well from which no production is desired andthe sections of drillable casing aresubstantially opposite portions ofthe well from which production is desired, securing a wash pipeinsidesaid casing string, said wash pipe extending throughout thedrillable sections and secured to said normal casing above and belowsaid drillable sections, cementing said casing, in the well, removingsaid Wash pipe from the well and drilling sections of drillable casingfrom portions of the well from which production is desired and baringthe surfaces of the'portions of the well from which the drillable casinghas been removed and from which production is desired.

4. A method of operating`a well comprising lowering into the well astring of casing made up of sections of normal casing and sections ofdrillable casing so that the sections of normal casing are substantiallyopposite portions of the v well from which no production is desired andthe sections of drillable casing are substantially opposite portions ofthe well from which production is desired, securing a wash pipe insidesaid casing string, said wash pipe extending throughout the drillablesections and secured to said normal casing above and below saiddrillable sections, ce menting said casing in the well, removing saidwash pipe from the well and drilling sections of drillable casing fromportions of the well from which production is desired, baring thesurfaces of the portions of the well from which the drillable casing hasbeen removed and from which production is desired, and lowering throughthe remaining sections of normal casing a perforated inner string seatedopposite portions of the well from which production is desired.

5. A method of operating a well comprising lowering into the well spacedapart sections of casing secured to a string of pipe of smaller diameterwithin said-sections of casing, said sections of casing being so spacedapart on said pipe of smaller diameter that they come to restsubstantially opposite portions of the well from which no production isdesired, cementing such sections of casing in such positions, removingsaid pipe of smaller diameter, and baring the surfaces of the portionsof the well from which production is desired.

6. A method of operating a well comprising lowering into the well spacedapart sections of casing secured to a string of pipe of smaller diameterwithin said sections of casing, said sections of casing being so spacedapart on said pipe of smaller diameter that they come to restsubstantially opposite portions of the Well from which no production isdesired, cementing. such sections of casing in such positions, removingsaid pipe of smaller diameter, baring the surfaces of the portions ofthe well from which production is desired, and lowering through theremaining sections of' normal casing a perforated inner string seatedopposite portions of the well from which production is desired.

7. The method of operating a well which penetrates spaced productivestrata which includes assembling in spaced relationship sections ofnormal casing, holding said sections by readily removable means ofsmaller diameter than said sections in such spaced relationship thatthey will be positioned in the well between the productive strata,positioning the assembly in the well and removing the readily removablemeans.

8. The method of operating a well which penetrates spaced productivestrata which includes assembling in spaced relationship sections ofnormal casing, holding said sections by readily removable means ofsmaller diameter than said sections in such spaced relationship thatthey will be positioned in the well between the productive strata,positioning the assembly in the well, cementing the normal casingsections in place between the productive strata, and removing thereadily removable means.

9. Casing adapted to be used in wells comprising spaced sections ofnormal casing and readily removable means holding the normal casingsections in assembled relation, said readily removable means being ofsmaller diameter than the normal casing sections.

10. Casing adapted to be used in wells comprising spaced sections ofnormal casing and readily removable casing sections connecting thenormal casing sections. said readily removable casing sections being ofsmaller diameter than the normal casing sections.

l1. A casing for use in wells comprising spaced sections of normalcasing, intervening sections formed of readily removable material, andreadily removable means extending longitudinally through the sectionsand connected thereto for holding said sections in assembled relationand against parting.

12. A casing for use in wells comprising spaced sections of normalcasing, intervening sections -formed of readily removable material, andav readily removable wash pipe v extending longitudinmy through thesections and connected thereto necting the sections of normal casing tosaid readily removable means to hold the sections in proper spacedrelationship thereon.

14. A casing for use in wells comprising spaced sections of normalcasing, a readily removable wash pipe extending therethrough, and meansconnecting the sections of normal casing to said readily removable washpipe to hold the sections I in properly spaced relationship thereon.

l5. The method of operating a. well which penetrates a plurality ofproductive strata which includes assembling spaced sections of normalcasing and one or more intervening sections of readily removable casing,holding the sections of normal casing against' separation by readilyremovable means extending-through the sections, lowering the assemblyinto a well to position the intervening sections opposite productivestrata, and removing the readily removable sections and said readilyremovable means.

16. The method of operating a well which penetrates a plurality ofproductive strata which includes assembling spaced sections of normalcasing and one or more intervening sections of readily removable casing,holding the sections of normal casing against separation by readilyremovable means extending through the sections,

lowering the assembly into a well to position the intervening sectionsopposite productive strata, cementing the normal casing sections inplace, and removing the readily removable sections and said readilyremovable means.

17. The method of operating a well which vpenetrates av plurality ofproductive strata which -includes mounting a plurality of sections ofnormal casing in spaced relation on a readily removable wash pipe,lowering the wash pipe and sections into a well and positioning thenormal casing sections between productive strata.

` 18. The method of operating a well which penetrates a plurality ofproductive strata which includes mounting a plurality of sections ofnormal casing in spaced relation on a readily removable Wash pipe',lowering the wash pipe and sections into a well and positioning thenormal casing sections between productive strata, and removing the washpipe.

19. The method of operating a Well which penetrates a plurality ofproductive strata which includes mounting a plurality of sections ofnormal casing in spaced relation on a readily removableV wash pipe,lowering the wash pipe and sections into a well and positioning thenormal casing sections between'productive strata, cementing the sectionsof normal casing in place and removing the wash pipe. 20. The method ofoperating a well which includes assembling sections of normal casingwith sections of readily removable casing, positioning the assembledcasings in the Well so that the sections of readily removable casingwill be opposite one or more productive strata, and removing theremovable sections by means of explosives leaving the normal casingsections in the well.

21. The method of operating a well which includes assembling sections ofnormal casing withA sections of readily removable casing, positioningtheassembled sections in the well so that the sections of readily'removable casing will be opposite one or more productive strata,cementing the normal casing sections in place, and removing by means ofexplosives the readily removable casing sections leaving the normalcasing sections in the well. j

RICHARD I. BROWN.

